Expert Gardener Rose Plant Food Fertilizer 12-6-10, 4 lb., contains a slow release nitrogen formula that feeds for up to 3 months. In addition to customized macronutrient levels of Nitrogen, Phosphorous, and Potassium this fertilizer also contains a customized mix of micronutrients such as Calcium, Magnesium, Sulfur, Iron, Manganese and Zinc. Micronutrients are essential elements every plant needs but are used by the plants in smaller amounts than the NPK macronutrients and are critical to overall plant health.